Wireless devices have grown in popularity and are now used in a wide variety of applications. However, wireless devices are generally more difficult to test (e.g., to verify design and measure performance and other parameters) than conventional wired devices. For example, wireless devices often allow mobility, which may create interactions between the physical and the protocol layers that significantly increase the complexity and number of tests necessary to verify a design relative to wired networks. Furthermore, wireless test systems, such as those for testing wireless local area network (WLAN) devices that use IEEE 802.11 standards, may require more complex protocols to address aspects that wired devices usually lack, such as dynamic configuration, the spatial nature of the system, and channel sharing by multiple stations.
There are a number of drawbacks to conventional approaches for testing wireless devices, especially for wireless devices that utilize space diversity or multiple-input multiple-output (MIMO) techniques. For example, one approach employs actual open-air environment testing, which is complex, expensive, requires large dedicated test areas (e.g., a large building), and may be very difficult to reproduce over time at different locations. Alternatively, an actual environment may be approximated using a network of passive devices (e.g., attenuators, phase shifters, and/or power dividers) and/or channel emulation devices with radio frequency up/down conversion, but this approach generally does not scale well, is complex to design and expensive to build, inflexible in terms of the range and variety of environments emulated, and may require a large amount of space and components, especially for the emulation of complex environments. Yet a third approach replaces this network of passive devices that emulates the environment with a combination of RF downconversion, baseband digital signal processing, and RF upconversion; while this approach is more flexible, it is expensive and does not scale well.
Another approach relies on computer simulation of the wireless device and the desired environmental parameters, but this approach is inherently limited and is not capable of performing measurements on the actual wireless device under test. As a result, there is a need for improved wireless device test techniques.